题目内容：

在那些选择题中,什么时候用need,must,could,may
比如说这两题
1.Be polite,You___talk ton the old like that.
A.couldn't B.needn't C.mustn't D.wouldn't
2.--Listen!Is Rose singing in the next room?--No,it___be.She has gone to Shanghai.
A.may not B.can't C.mustn't D.needn't
说明一下理由
C B
再想想

优质解答

a b
1题needn't 是没必要 语境不对
mustn't是禁止 更不对
这里是表能力 couldn't 就是不能
2题用can't 是表推测 肯定不的意思
建议你问问老师情态动词